Cancer incidence was investigated in a cohort of 700 workers employed at a Connecticut chemical plant between mid-1965 and 1989.

The plant produced a variety of chemicals, including arylamines such as dichlorobenzidine (DCB), o-dianisidine, o-tolidine, but not benzidine.

Benzidine production ceased prior to mid-1965.

The principal finding was a statistically significant increase in the standardized incidence ratio (SIR) for bladder cancer in men (SIR=8.3 ; confidence interval, 3.3 to 17.0).

Based on an exposure classification system developed by a panel of former and current employees, the observed association between bladder cancer cases and exposure to arylamines increased with increasing exposure (SIRs=0.0,5.5,16.4, for none, low, or moderate levels of exposure, respectively).

Smoking probably contributed to the bladder cancer risk, as all case subjects were known to be current or former cigarette smokers.